The aim of this project is to quantify the extent to which modifications of the swallow response can be provoked by the systematic variation of bolus volume, viscosity, and temperature as well as by pre-swallow thermal stimulation and volitional manipulation of the act of swallowing. Data will be collected on groups of volunteer subjects in the 20-29, 40-49, 70-79, yr age brackets. The two older groups were selected to provide a normal data base for a planned comparison with stroke victims who cluster in these decades. The younger group completes the age spectrum facilitating analysis of age effects on the swallow response and also serves as a willing group of subjects on whom to experiment with volitional control. Several protocols are described using videofluoroscopy concurrently with pharyngeal manometry as subjects swallow a spectrum of volumes, viscosities, and pills. Volitional maneuvers to be studied include those suggested to be of use in dysphagic patients: breath holding at peak inhalation, prolonged laryngeal elevation, and forceful swallowing. Furthermore, the effect of pre-swallow thermal stimulation will be systematically evaluated and compared to manipulations of bolus temperature. Manometric and videofluoroscopic data will be synchronized and recorded. Data analysis will utilize new techniques of computer assisted video and manometric analysis. A major thrust of the fluoroscopy analysis will be to incorporate motion analysis as well as timing analysis. Data on each parameter for each swallow will be numerically expressed in spreadsheets organized with 0.03 sec time intervals as the column headings and rows for data parameters. This analytic method allows for critical comparisons of concurrent events as well as establishing a comprehensive data set for comparison in the evaluation of dysphagic patients. Furthermore, mechanisms whereby therapeutic maneuvers and pre-swallow stimulation may benefit dysphagia will be described. Thus, the plasticity of the pharyngeal swallow in terms of the range of motion and timing of motion of oropharyngeal structures as affected by bolus-related variables, age, and volitional control is that the pharyngeal swallow can be conceptualized as being composed of several closely coordinated, but potentially modifiable components, rather than as a single stereotyped event. The protocols described examine the extent to which normal subjects are capable of varying cricopharyngeal opening, laryngeal closure, peristaltic force, and bolus propulsion. The significance of these findings relates to therapeutic strategies applied to dysphagic individuals. An impaired patient may have trouble with one aspect of the swallow such as laryngeal closure or upper esophageal sphincter opening, but still be capable of oral feeding if that defect can be selectively compensated for.